Search Results (1,201)

Based on ongoing experimental research, the present manuscript presents the effect of the slippage of a steel reinforcing bar due to corrosion on the chord rotation and deformation of corroded Reinforced Concrete members. The experimental results recorded that the increase in the corrosion level of the steel led to bond strength loss and relative slip between the steel and concrete, which was increased from 1.5 mm in non-corroded conditions to 3.5 mm even at low corrosion levels, up to a 5% steel mass loss. This slippage of corroded reinforcing bars from the anchorage leads to a proportional increase in terms of chord rotation due to pull out resulting in an additional increase in the displacement of the column’s top. In conclusion, the present study highlights the great importance of the contribution of the resulting slippage of a steel reinforcing bar due to corrosion in the calculation of the limit chord rotation (column–beam), a term which is of major importance in the assessment of the structural integrity of old RC structures, which was introduced as an adequacy requirement by both Eurocode 8-3 and the Greek Code of Structural Interventions (KAN.EPE). Full article

Steel and prestressed concrete traction poles can be fixed to reinforced concrete pile foundations using typical bolted connections. The stainless steel fastening screw is connected to the ordinary steel foundation pile reinforcement by friction welding under specific friction welding process parameters. From the perspective of the structural strength of the connection between the traction pole and the foundation pile, regarding the transfer of tensile and shear forces through a single anchor bolt, the yield strength of stainless steel bolts should be R_e,min ≥ 345 MPa for M30 anchors, R_e,min ≥ 310 MPa for M36 anchors and R_e,min ≥ 300 MPa for M42 anchors. This requirement is reliably met by martensitic stainless steels, while other stainless steels have yield strengths below the required minimum. What truly determines the foundation pile’s load capacity is not the satisfactory mechanical strength of the stainless steel (here, the parameters are met), but the quality of the friction-welded end connection between the reinforcement and the threaded bars. Incorrect selection of the type of prestressing steel in the analyzed connection can have enormous consequences for foundation pile manufacturers. Annual production of foundation piles amounts to thousands of units, and an incorrect decision made by the pile designer at the design stage can result in significant financial losses and a high risk to human life. This article presents the results of studies on friction-welded connections of M30, M36, and M42 threaded bars made of austenitic 1.4301 (AISI 304) and martensitic 1.4021 (AISI 420) stainless steel with B500SP reinforcement bars. The tests yielded negative results for 1.4021 (AISI 420) steel, despite its yield strength exceeding R_e ≥ 360 MPa. Full article

In accelerated bridge construction, precast concrete girders are connected to cast-in-place concrete slab using shear transfer reinforcement across the interface plane to ensure the composite action. The steel transverse reinforcement is prone to severe corrosion due to the extensive use of de-icing salts and severe environmental conditions. As glass fiber-reinforced polymer (GFRP) reinforcement has shown to be an effective alternative to conventional steel rebars as flexural and shear reinforcement, the present research work is exploring the performance of GFRP reinforcements as shear transfer reinforcement between precast and cast-in-place concretes. Experimental testing was carried out on forty large-scale push-off specimens. Each specimen consists of two L-shaped concrete blocks cast at different times, cold joints, where GFRP reinforcement was used as shear friction reinforcement across the interface with no special treatment applied to the concrete surface at the interface. The investigated parameters included the GFRP reinforcement shape (stirrups and headed bars), reinforcement ratio, axial stiffness, and the concrete compressive strength. The relative slip, reinforcement strain, ultimate strength, and failure modes were reported. The test results showed the effectiveness and competitive shear transfer performance of GFRP compared to steel rebars. A shear friction model for predicting the shear capacity of as-cast, cold concrete joints reinforced by GFRP reinforcement is introduced. Full article

Grouted sleeves are commonly used to connect prefabricated structural components, but construction defects can easily occur after installation, posing potential risks to the structure. This study conducts comparative uniaxial tensile tests on 39 grouted-sleeve specimens in 13 groups—including standard specimens, defective specimens, and specimens repaired with supplementary grouting. The strain distribution patterns under different grouting lengths and loading levels are analyzed to investigate the load-transfer mechanism between reinforcement bars and grouted sleeves, as well as the influence of various supplementary grouting amounts and material strengths on the mechanical performance of defective sleeves. In the uniaxial tensile test of grouted sleeves, with grout strengths of 85 MPa and 100 MPa and HRB400-grade steel bars, when the grouted anchorage length was 4 d, insufficient anchorage length resulted in low bond strength between the grout and the steel bar, leading to bond–slip failure. When the grouted anchorage length reached 6 d, steel bar fracture occurred inside the sleeve. When the total anchorage length formed by two grouting sessions reached 8 d, specimen slippage decreased, showing a trend where the strain growth rate of the sleeve gradually decreased from the grouted end to the anchored end, while the strain growth rate of the steel bar gradually increased. The longer the total anchorage length in the sleeve after grout repair, the stronger its anti-slip capability. The bearing capacity and failure mode of the specimens depend on the strength of the steel bars connected to the grouted sleeves and the strength of the threaded connection ends at the top. Experimental results show that the anchorage length and strength of high-strength grout materials have a significant reinforcing effect on defective sleeves. The ultimate bearing capacity of specimens with anchorage length of 6 d or more is basically the same as that of steel bars. Specimens with a total anchorage length of 8 d show approximately 10~20% less slippage than those with 6 d. The safe anchorage length for HRB400-grade steel bars in sleeve-grouted connections is 8 d, even though the bearing capacity of grouted sleeves with a 6 d anchorage length already meets the requirements. Bond strength analysis confirms that the critical anchorage length is 4.49 d. When the grouted anchorage length exceeds the critical length, the failure mode of the specimen is steel bar fracture. When the grouted anchorage length is less than the critical length, the failure mode is steel bar slippage. This conclusion aligns closely with experimental results. In engineering practice, the critical anchorage length can be used to predict the failure mode of grouted sleeve specimens. Based on experimental research and theoretical analysis, it is clear that using grout repair to reinforce defective grouted sleeve joints with a safe anchorage length of 8 d is a secure and straightforward strengthening method. Full article

Concrete structures suffering from Mg²⁺ environments may suffer severe damage, which mainly has something to do with the coupled effect among Cl⁻, SO₄²⁻, and Mg²⁺. Based on a systematic review of Web of Science and Scopus database (2000–2025), we first summarized the migration behavior, reaction paths, and interaction mechanism of Cl⁻, SO₄²⁻, and Mg²⁺ in cementitious matrices. Secondly, from the perspective of Cl⁻ cyclic adsorption–desorption breaking the passivation film of steel bars, SO₄²⁻ generating expansion products leads to crack expansion, then Mg²⁺ decalcifies C-S-H and transforms into M-S-H; we analyzed the main damage mechanisms, respectively. In addition, under the coexistence conditions of three kinds of ions, the “fixation–substitution–redissolution” process and “crack–transport” coupling positive feedback mechanism further increase the development rate of damage. Then, some anti-corrosion measures, such as mineral admixtures, functional chemical admixtures, fiber reinforcements, surface coatings, and new binder systems, are summarized, and the pros and cons of different anti-corrosion technologies are compared and evaluated. Lastly, from two aspects of simulation prediction for the coupled corrosion damage mechanism and service life prediction, respectively, we have critically evaluated the advances and problems existing in the current research on the aspects of ion migration-reaction coupled models, multi-physics coupled frameworks, phase-field methods, etc. We found that there is still much work to be conducted in three respects: deepening mechanism understanding, improving prediction precision, and strengthening the connection between laboratory test results and actual projects, so as to provide theoretical basis and technical support for the durability design and anti-corrosion strategies of concrete in complex Mg²⁺ environments. Full article

This study presents a comparative investigation of the dynamic compression behaviors of steel fiber-reinforced cementitious composites (SFRCC) and steel fiber-reinforced concrete (SFRC) under elevated temperatures up to 800 °C, utilizing a split Hopkinson pressure bar (SHPB). The experimental results demonstrate that SFRCC exhibits enhanced overall performance at high temperatures, maintaining a progressive failure mode and approximately 40% residual strength even at 800 °C, while SFRC experiences rapid deterioration beyond 600 °C. In the low-to-medium temperature range of 200–400 °C, SFRCC shows significantly higher dynamic peak stress and toughness compared to SFRC. However, in the high-temperature range of 600–800 °C, the superior thermal stability of the aggregate–matrix system in SFRC results in better performance in these metrics. The findings provide insights into the damage evolution mechanisms of fiber-reinforced cement-based materials under coupled thermal and dynamic loads, offering a critical theoretical foundation for material selection in engineering structures exposed to extreme thermal environments. Full article

The consumption of energy and sports drinks is on the rise globally, exposing dental restorations to more frequent low-pH challenges, which affect degradation. This in vitro study simulated the combined effect of energy drink exposure and cyclic fatigue loading on the fatigue survival rate and flexural strength of three direct dental resin restorative materials with distinct chemistries: a bioactive ionic resin (Activa Presto), a giomer (Beautifil Flow Plus F00) and a conventional nano-hybrid composite (Tetric Ceram). Bar-shaped specimens (25 × 2 × 2 mm) were fabricated according to ISO 4049 and stored for 24 h in either distilled water or 0.2 M citric acid (pH ≈ 2.5), simulating an energy drink (n = 10/group). The samples then underwent chewing simulation (40 N, 100,000 cycles, 1.6 Hz) using a steel antagonist; surviving specimens were tested via three-point bending to determine their flexural strength. All the materials were affected by storage conditions: Activa Presto showed the lowest fatigue survival (20% in water; 0% in citric acid), Tetric N-Ceram moderate survival (40% in both solutions) and Beautifil Flow Plus F00 the highest and most stable survival (90% in water; 40% in citric acid). Among the surviving specimens, Tetric Ceram exhibited the highest flexural strength, followed by Beautifil Flow Plus F00 and then Activa Presto. Citric acid exposure and cyclic loading adversely affected the mechanical performance of all the materials within the limitations of this study. Full article

Data-driven quality control (QC) systems for the hot forming of steel parts increasingly rely on deep learning models deployed at the network edge, making multivariate sensor time series a critical asset for both local decisions and management information system (MIS) reporting. However, these models are vulnerable to adversarial perturbations and realistic signal disturbances, which can induce misclassification and distort key performance indicators (KPIs) such as first-pass yield (FPY), scrap-related losses, and latency service-level objectives (SLOs). To address this risk, this study introduces a Digital-Twin-Conditioned Diffusion Purification (DTCDP) framework that constrains latent diffusion-based denoising using process states from a lightweight digital twin of the hot-forming line. At each reverse-denoising step, the twin provides physics residuals that are converted into a scalar penalty, and the diffusion latent is updated with a guidance term. This directly bends the sampling trajectory toward reconstructions that adhere to process constraints while removing adversarial perturbations. DTCDP operates as an edge-side preprocessing module that purifies sensor sequences before they are consumed by existing long short-term memory (LSTM)-based QC models, while exposing purification metadata and physics-guidance diagnostics to the plant MIS. In a four-week production dataset comprising more than 40,000 bars, with white-box ℓ∞ attacks crafted on multivariate sensor time series using Fast Gradient Sign Method and Projected Gradient Descent at perturbation budgets of 1–3% of the physical range, combined with additional realistic disturbances, DTCDP improves the robust classification performance of an LSTM-based QC model from 61.0% to 81.5% robust accuracy, while keeping clean accuracy (≈93%) and FPY on clean data (≈97%) essentially unchanged. These results indicate that physics-aware, digital-twin-guided diffusion purification can enhance the adversarial robustness of edge QC in hot forming without compromising operational KPIs. Full article

This study investigates the development of adiabatic shear bands (ASBs) in AISI 1045 carbon steel under high-strain-rate uniaxial compression, emphasizing the conditions governing their onset and growth. Split Hopkinson pressure bar (SHPB) experiments were carried out at strain rates of 1000, 2000 and 4000 s⁻¹ with controlled displacement/strain interruption to capture gradual ASB formation throughout the process. Stress–strain data were analyzed alongside optical microscopy to determine the critical strain for ASB initiation, document ASB morphology, dimensions and type, and connect ASB formulating stages to material macroscopic mechanical behavior. The observations clarify how deformation evolves from homogenous plastic flow to localized shear instability as the strain and strain rate increase, linking mechanical response to microstructural features. Integrating these results, the effects of strain rate and strain progress on ASB formation and evolution characteristics are investigated. These findings enhance our understanding of shear localization phenomena under dynamic loading and provide a basis for predicting failure modes in structural applications. Full article

With the advancement of welding technology, the demand for 70S-6 welding wire steel has steadily increased in industries such as construction, automotive, pressure vessels, and line pipe manufacturing. To optimize the production process of the target material, this study utilized the finite-element software ABAQUS to numerically simulate the multi-pass finish rolling process of 70S-6 welding wire steel. The study investigates the effects of the key rolling parameters—pass distribution (8/10/12 passes), finish rolling temperature (860/880/900 °C), and rolling speed (0.5 Vp/1.0 Vp/1.5 Vp, here Vp denotes the reference industrial rolling speed) on the rolling force, temperature field, and equivalent stress/strain during finish rolling. The results show that the increased number of passes homogenizes deformation, reduces local stress concentration and enhances mechanical properties. Specifically, 12 passes reduce the peak rolling force from 250,972 N to 208,124 N, significantly enhancing stress and temperature uniformity across the section. Increasing the finish rolling temperature lowers the pass-averaged flow stress and attenuates rolling-force fluctuations. At 880 °C, the simulated core–surface temperature gradient is minimal (50 °C), whereas at 900 °C the gradient increases (80 °C) but the rolling-force histories exhibit a lower peak level and smaller low-frequency oscillations; thus 880 °C is preferable when through-thickness thermal uniformity is targeted, while 900 °C is more suitable when a smoother load response is required. Increasing the finish rolling speed from 0.5 Vp to 1.5 Vp reduces the peak rolling force from 233,165 N to 183,665 N and significantly damps low-frequency load oscillations. However, it concurrently intensifies stress localization at the outer-surface tracking points P3/P4, which are in direct contact with the rolls, where the local equivalent stress approaches 523 MPa, even though the overall strain distribution along the bar length becomes more uniform. Overall, the optimal processing window is identified as a 12-pass schedule, a finish rolling temperature of 880–900 °C, and a rolling speed of 1.0–1.5 Vp, which can improve both rolling quality and temperature and stress and strain uniformity. Full article

A trussed concrete-filled square steel tubular (CFSST) composite column frame is proposed for multi-story residential buildings. The frame provides high lateral resistance and can be integrated within wall systems. To evaluate its seismic performance, three full-scale specimens were subjected to quasi-static cyclic loading. The failure modes, load-carrying capacity, stiffness degradation, and energy dissipation characteristics were examined and compared. The results show that, compared to the H-shaped steel column frame (HK) with equivalent steel consumption, the trussed CFSST composite column frame exhibits an 88.3% increase in yield load and an 87.1% increase in peak load, together with significant improvements in stiffness and energy dissipation. Compared with an ordinary CFSST column frame (FK), the proposed system required 41% more steel but attained a 56% increase in load-carrying capacity, along with corresponding enhancements in stiffness and energy dissipation. Finite element (FE) models were developed based on the experimental results, and parametric analyses were performed to investigate the effects of corner-end column spacing, number of truss diagonal bars, truss joint type, axial compression ratio, and steel strength. Design recommendations are provided accordingly. Full article

This study investigates the tribological response of basalt, carbon, and basalt–carbon hybrid laminates subjected to pressurized water-immersion aging and reciprocating sliding, with emphasis on the role of stacking sequence. Composite plates with B₈, C₈, B₂C₄B₂, and C₂B₄C₂ architectures were aged in deionized water at 10 bar for up to 30 days, then tested against a 100Cr6 steel ball at 30 N, 50 m track and 1 or 2 Hz. Water uptake ranged from approximately 4.3% for B8 to 1.2–2.7% for carbon-rich and hybrid laminates, and induced a depression and broadening of the epoxy glass-transition region that was most severe in basalt-skinned systems. At 1 Hz and 30-day aging, B8 exhibited the most severe damage, with wear-scar widths and depths approaching 3.0 mm and 0.50 mm, whereas C8 retained narrow shallow scars below 0.8 mm and 0.02 mm and COF values below 0.20. Increasing frequency to 2 Hz mitigated wear, reducing B8 depth to approximately 0.30 mm under similar conditions. Factorial analysis attributed more than 70% of the variance in wear width to laminate architecture. The combined pressurized immersion, multi-frequency reciprocating wear and DSC, profilometry, and SEM methodology provides an original framework to link hygrothermal plasticization to architecture-dependent tribological durability in hybrid basalt–carbon laminates. Full article

This study investigates the cyclic behavior of reinforced concrete beam–column joints strengthened with hybrid GFRP–steel reinforcement using nonlinear finite element analysis. Six hybrid configurations—defined by varying the percentage of the total longitudinal steel reinforcement area, in the beam, replaced with GFRP bars (0%, 20%, 25%, 33%, 50%, and 100%)—were evaluated in terms of load–displacement hysteresis, stiffness degradation, dissipated energy, and crack development. A multi-criteria decision analysis (MCDA) was employed to quantitatively compare the six configurations. The findings demonstrate the potential of partial GFRP substitution to enhance the seismic performance of reinforced concrete beam–column joints. Full article

In this study, with the rapid development of the field of rail vehicles, the laser welding process with high energy and small thermal deformation is selected, which reduces the working hours of post-welding grinding, repainting, and other processes, and ensures the industrial design requirements of the beautiful body after welding. The welding process for the non-penetration laser lap welding of SUS301L stainless-steel plates was optimized to address the problem of welding marks on the outer surface of railway vehicle car bodies. The impact of laser power, welding speed, and defocusing amount on weld penetration and tensile shear load was investigated using the response surface methodology. The results showed that the optimal response model for tensile shear load was the linear model, while the optimal response model for weld penetration was the 2FI model. The defocusing amount had the greatest influence on tensile shear load and weld penetration. When the laser power was 1.44 kW, the welding speed was 15 mm/s, and the defocusing amount was −4 mm, the tensile shear load reached its maximum by prediction. The actual tensile shear load of welded joints using these parameters was 4293 N with an error of merely 0.31% relative to the predicted value. The shear strength of laser-welded joints was measured at 429.3 N/mm, meeting the criteria established by the relevant standards. The tensile fracture shows characteristics of brittle fracture. The surface of the welded joints was bright white and well-formed, while the back side of the lower plate exhibited no signs of melting or welding marks. The microstructure of the weld zone (WZ) exhibited irregular columnar austenite and plate-like ferrite, while the heat-affected zone (HAZ) comprised columnar austenite and elongated bars or networks of δ-ferrite. The small-angle grain in welded joints can reduce grain boundary defects and mitigate stress concentration. After welding, angular deformation occurred, resulting in a residual stress distribution that shows tensile stress near the weld and compressive stress at a distance from the weld. Full article

Currently, there are several deep drill geothermal projects that aim to discharge superheated or supercritical geothermal fluid for sustainable power production. In geothermal power utilisation, the well casing steel and surface equipment is susceptible to corrosion due to corrosive species in the geothermal fluid. The temperature and the phase state of the fluid greatly affect the extent and the forms of corrosion that can occur. To mitigate corrosion damage in the casing and surface equipment, the recently developed production method Extra High-speed Laser Application (EHLA) cladding is proposed as a solution. To simulate application of carbon steel and EHLA clads in superheated geothermal wells, the materials were tested in a superheated steam containing CO₂ and H₂S at 450 °C temperature and 150 barG pressure. Microstructural and chemical analysis was performed with SEM, EDX and XRD, and corrosion rate was analysed with the weight loss method. The carbon steel was prone to corrosion with a double corrosion layer but the corrosion of the EHLA clads was insignificant. The results show that the EHLA clads tested have good corrosion resistance in the test environment, and the study can aid in the selection of casing and clad materials for future deep geothermal wells. Furthermore, this study shows that the EHLA clads increase the variety of corrosion mitigation solutions for future geothermal projects. Full article